Feature: Add rawtext flag to Mapping

[MartinWitt]

Currently for regex replacements the user needs to escape the string.
e.g.

	mapping = {
		from = "adapterFactory.dispose\\(\\);"
		to = "\\(\\(IDisposable\\) \\(adapterFactory\\)\\).dispose\\(\\);"
	}

This leads to easy faults and mistakes. A raw text flag could reduce the visual clutter. A solution to reduce this could be either Pattern.quote() or in the future a use of java 14 RawTextLiterals. Adding a flag in e.g. Mapping``boolean rawtext = false with default value false would keep the behavior of existing configs the same, but allows newer configs to profit from this change. A config entry with the new flag could like this. Increased readability and more fault tolerant.

	mapping = {
                rawText = true
		from = "adapterFactory.dispose();"
		to = "((IDisposable) (adapterFactory)).dispose();"
	}

wdyt about this improvement?